Lidl's , Just looked at bottle does not say how many litres I reckon about 3 . On the bottle it states 40+ washes! Cost I think was about £2.50. Where it says 40 washes I would think that about 40 emptyings!!

That is what I use a dollop is all that is needed as too much gives off a chemically smell, it breaks down lumpy bits and keep the bugs eating away all that goes out is liquid, safe for cesspools the Formaldehyde based and the replacement one kills the cesspit, DEAD.
That is why they do not like it in toilet systems at shows and rallies.